The present invention relates to a storage apparatus to be connected, for example, to a computer apparatus such as a main frame. The present invention also relates to a virtual tape apparatus which uses a hard disk, etc. in place of a magnetic tape.
In known computer systems, a tape library apparatus has mainly been used for backup of the information stored in the hard disk. The tape library apparatus has high memory capacity on the order of giga-bits or tera-bits by loading a plurality of magnetic tapes. However, existing magnetic tape employs a format in which one file is stored in a volume of magnetic tape. Therefore, when the capacity of a file to be backed up is smaller than the storing capacity of one volume of a magnetic tape, only a part of the magnetic tape is used for storing data. Accordingly, the total medium cost rises. Moreover, when one file is stored in one volume of magnetic tape, the number of magnetic tapes must be increased to the number of files to be backed up. In this case, the size of the tape library becomes high.
Therefore, in order to reduce the medium cost of the magnetic tape, a tape apparatus having a multi-file function has also been developed. The multi-file function realizes storing of a plurality of files to a volume of magnetic tape. However, when the multi-file system is introduced, a host computer is required to conduct complex management, for example, history management and catalog management. Also, a problem in operation is created because the multi-file system cannot be applied to the files to be used simultaneously.
Moreover, access to the magnetic tape is realized at a lower speed than that of the hard disk. Therefore, in the current situation where the amount of data is increasing rapidly, the time required for backup utilizing the magnetic tape also becomes remarkably long. The longer time required for backup jobs causes delays and perhaps other trouble in regular jobs.
Considering the circumstances explained above, recently, a virtual tape apparatus has been developed in which a hard disk, which can make access at higher speed than the magnetic tape, may be used in place of the magnetic tape.
In this virtual tape apparatus, the tape apparatus is virtually emulated on the hard disk within the disk subsystem connected to the host computer. Therefore, the virtual tape apparatus utilizes, as it is, the technology of the tape apparatus to make access to a storage medium at a speed higher than that of the actual tape apparatus.
In a virtual tape apparatus, a disk subsystem writes (stage out) a plurality of virtual tape volumes from the hard disks to a single actual tape on the occasion of writing the virtual tape volume stored in the hard disk to the actual physical tape (a physical tape is called a xe2x80x9creal tapexe2x80x9d). Thereby, in the virtual tape apparatus, the number of actual tapes required is reduced as much as possible and thereby reduction in size of the tape library can be realized and reduction of medium cost can also be realized.
In the virtual tape apparatus of the related art, a plurality of tape volumes are written on the same real tape in some cases. In this case, a virtual tape apparatus is sometimes required to read all of the contents of the real tape. Thereby, the performance of the virtual tape apparatus may be identical or rather deteriorated in comparison with the performance when the virtual tape apparatus is not provided and data is read in direct from the real tape volume.
The present invention has been proposed considering the background explained above. It is an object of the present invention to provide a new and improved storage apparatus consisting of a virtual tape apparatus which may be more effectively accessed from a host computer.
A tape volume can be given an attribute depending on its operation mode, to eliminate disadvantages of the virtual tape apparatus of the related art. In fact, it is better to form the groups of the virtual tape volumes depending on a selected attribute thereof. In known systems, though, some tape volumes are used periodically and some are not, and are mounted simultaneously or individually. However, in the virtual tape apparatus of the related art, the virtual tape volumes are not handled by discriminating based on the attribute thereof.
In view of attaining the object explained above, a storage apparatus is provided between a tape storage apparatus having a plurality of tape storage media and a driving mechanism, and a host computer, to store the data exchanged between the host computer and tape storage apparatus as a virtual tape volume. A virtual storage area is provided for storing virtual tape volumes, a data transfer control means controls data transfer among the virtual storage area, host computer and tape storage apparatus, and a database stores information regarding the selected attribute of the virtual tape volume. The data transfer control means forms groups of the virtual tape volumes having the identical attribute and identifies, when the host computer has issued a request to any one of the virtual tape volume groups, the other virtual tape volumes are included in the virtual tape volume group.
According to the present invention, the virtual tape volume groups are developed previously in the virtual storage area. Therefore, when a host computer has issued a request to the virtual tape volume in such a group, the response rate to this request can be improved.
The storage apparatus can be provided between a tape storage apparatus having a plurality of tape storage media and a driving mechanism, and a host computer. The storage apparatus stores the data exchanged between the host computer and tape storage apparatus as the virtual tape volumes. This aspect of the invention includes a virtual storage area for storing virtual tape volumes, a data transfer control means for controlling data transfer among the virtual storage area, host computer and tape storage apparatus, a database for storing information regarding at least one attribute of the virtual tape volumes, a virtual special tape volume collecting and recording the information regarding attributes of all virtual tape volumes, and a means for reflecting the contents of changes of virtual special tape volumes edited by the host computer on the information regarding the attributes of virtual tape volumes stored in the database.
According to this aspect of the present invention, the host computer edits the virtual special tape volumes. The host computer reflects contents of changes of the edited virtual special tape volumes on the information regarding the attributes of the virtual tape volumes stored in the database. Thereby, the host computer can automatically edit the attributes of the virtual tape volumes.